1. Field of the Invention
The present invention relates to the field of semiconductor device manufacturing and, more particularly to an inductive-coupled plasma apparatus employing a capacitive shield to reduce sputter contamination and a method for manufacturing the shield.
2. Description of the Background Art
The uniform and rapid processing of materials using induction generated, plasma-based processes (also referred to as inductive-coupled plasma processes) is important in the fields of semiconductor device manufacturing, packaging, optics, and the like. Many plasma processes are extensively used for the depositing or reactive etching of layers during semiconductor device fabrication. Especially, a radio frequency (RF at about 13.56 MHz ) induction plasma source is known to produce high electron density plasma, thus providing high processing rates.
For example, a semiconductor substrate is disposed within an evacuated chamber coupled to a source of plasma. By appropriately biasing the substrate, the plasma is coupled to the substrate for ion bombarding the substrate, for etching patterns in the substrate, or for depositing ions on the substrate to grow layers of selected materials thereon.
Hereinafter a conventional inductive-coupled plasma apparatus 10 shown in FIG. 1 and FIG. 2 is explained in detail. The conventional inductive-coupled plasma apparatus includes a process chamber 20 and a RF housing 40 which is often called a match box. The process chamber 20 includes a supporter 22 for supporting at least one semiconductor wafer 28, an edge ring 24 surrounding the supporter 22 and a gas injection ring 26 for injecting gas into the process chamber 20. Also the process chamber 20 further includes a pump 30 for controlling a pressure of an inner space of the process chamber 20.
A spiral coil 44 shown in FIG. 2 is coupled to the RF housing 40. Power is supplied from RF power supply line 48 to the spiral coil 44. The spiral coil 44 is supported by a coil holder 46, which is fixed to the RF housing 40 through a rod 80. The spiral coil 44 is separated from the plasma by a planar dielectric window 42.
However, in this conventional apparatus, high potentials on the coil cause some degree of capacitive coupling. Therefore, some particular regions, especially regions located underneath the coil on the surface of the planar dielectric window, are etched more excessively than other regions. Thus the etching process is contaminated due to falling particles from the etched regions of the planar dielectric window.
A technique is thus desired for maintaining high inductive coupling between the coil and the plasma, so that improved processing rates and reduction of sputtered contaminates from the dielectric window may be realized.